HUMAN REPRODUCTION

Purpose

• Produce offspring

• Gametes – sex cells or germ cells– Sperm– Secondary oocyte ( egg)

• Gonads – sex organs– Testes– Ovaries

• Supporting structures – assist the delivery and joining of the gametes– Penis– Uterus

• Female as additional supporting structures– Nurture the developing fetus

• zygote

• Female role – produce ova and provide environment of developing fetus

• Male role – production of sperm

Male reproductive organs

Functions of the male reproduction system

• Testes: – Exocrine function - produce sperm– Endocrine function - produce testosterone

• Ducts: transport, store, and assist in maturation of sperm

• Accessory sex glands: secrete most of the liquid portion of semen and excretion of urine.

External genitalia

• Scrotum

• Penis• Shaft• Glans penis• prepuce

• Testes– Seminiferous tubules– Interstitial cells

• Epididymis

Duct system

• Vas deferens– Ductus deferens– Spermatic cord

• Ejaculatory duct

• Urethra– Meatus

•

Semen

• Provides the transport medium, nutrients that protect sperm and facilitate their movement through the reproductive tract.

Three glands

• Seminal vesicles– Fructose– Prostoglandins

• Prostate gland

• Cowpers gland– Bulbourethra gland

Semen

• Volume in typical ejaculation – 2.5 to 5 ml

• 50 to 150 million sperm per milliliter

• pH 7.2 to 7.7

• # of sperm below 20 million, the male is likely to be infertile.

• Milky appearance – prostate

• Sticky consistency – seminal vesicles and bulbourethral glands

During sexual stimulation

• Sperm enter urethra from van deferens– Ejaculatory duct

• Seminal fluid enters

• Rhythmic muscle contraction cause semen to be expelled from penis in spurts

• Orgasm

• Refractory period

Testes

• Development

• spermatogenesis

Parts of sperm

• Head

• Middle

• tail

Changes in males

• Normal state – penis is flaccid– Sympathetic impulses cause vasoconstriction

of its arteries thus limiting blood flow

• Sexual excitement– Erection – 1st noticeable sign

• Parasympathetic impulses cause release of neurotransmitters and local hormones along with the gas nitric oxide. ‘these relax smooth muscles in the penal arteries. The arteries dialate and blood enters the blood sinuses. These spaces expand and compress the veins that drain the penis.

• Plateau stage – head of penis increase in diameter and vasocongestion causes the testes to swell.

• Orgasm – sympathetic impulses cause peristaltic contractions of smooth muscle in the walls of the ducts and glands. This propels sperm and fluid into the urethra.

• Sphincter at the base of the urinary bladder closes so no urine is released during ejaculation

• Penis returns to its flaccid state when the arteries constrict and pressure on the vein is relieved.

Male hormones

• Hypothalamus – Secretes GnRH

• Pituitary secretes– FSH– LH

FSH and LH

• Follicle stimulating hormone

• Promotes production of sperm in seminiferous tubules

• Luteinizing hormone• Also called ICSH –

interstitial cell stimulating hormone

• Controls the production of testosterone by the interstitial cells

spermatogenesis

• Development of sperm cells within seminiferous tubules

• Begins with puberty (around age 14 )

• Continues throughout life

Testosterone

• Stimulates spermatogenesis

• Responsible for maturation of reproductive system

• Responsible for secondary sex characteristics

Female reporductive system

Functions of the female reproductive system

• Ovaries produce– 2ndary oocytes, estrogens, progesterone,

inhibin, relaxin

• Utrine tube – Trsnports 2ndary oocyte to uterus– Site of fertilization

• Uterus – site of implantation– Development of fetus

• Vagina:– Receives the penis during sexual intercourse – Passage for childbirth

• Mammary glands– Synthesize, secrete, and eject milk

• Ovary / ovaries

• Fallopian tube

• Uterus

• Cervix

• Fagina

External genitalia

• Mons pubis – an elevation of adipose tissue covered by coarse pubic hair. Serves to cushion the pubic symphysis

• Two longitudinal folds of skin– Labia majora – develops from the same embryonic tissue as the

scrotum– Labia minora

• Prepuce of the clitoris – layer of skin at the point where the labia minora unite and cover the clitoris

• Clitoris• Hymen

Oogenesis

• Begins in females before they are born

• Females have all the eggs they will ever have by birth

• During fetal development meiosis I begins

• After puberty, hormones secreted by the anterior pituitary stimulate the resumption of oogenesis each month. Oocyte will complete the 1st meiotic division

• Ovulation – release of ovum form ovary

• After fertilization, meiosis II resumes.

• The nuclei of the sperm cell and the ovum unite , forming the zygote.

Changes in females

• 1st signs due to vasocongestion: – Engorgement of vaginal connective tissue with blood

during sexual excitement– Lubricating fluid oozes from capillaries and seeps into

epithelial layer– Glands within cervical mucosa secrete lubricating

mucus– parasympathetic impulses trigger erection of the

clitoris, vasocongestion of the labia, and relaxation of vaginal smooth muscels

– Vasocongestion causes breasts and nipples to become erect

• Plateau state – vasocongestion causes– the vaginal tissue to swell, narrows

opening– Vagina grips the penis more firmly– Orgasm may occur ( 3 to 15 rhythmic

contractions of the vagina, uterus, and perineal muscles)

Ovary

• handout

Ovarian cycle

Uterine cycle

• Menses

• Proliferative phase

• Secretory phase

Pregnancy

Menopause

• 1 year without menstruation

• Age 45 to 55

Birth control

• Rhythm method

• Withdrawal

• Tubial ligation

• vasectomy

Disease/disorders

• Circumcision – are there any medical benefits?

• Cryptorchidism• Hysterectomy• Episiotomy• Erectile dysfunction• Cervical cancer• Prostate cancer